Uncured gelcoat tips?

Discussion in 'Boatbuilding' started by mrdebian, Nov 16, 2021.

  1. mrdebian
    Joined: Apr 2021
    Posts: 26
    Likes: 4, Points: 3
    Location: Greece

    mrdebian Junior Member

    Hi all,

    One of my colleagues paint with less catalyst a kayak mold and the gelcoat doesn't seem to get cured even after 7 days at 12-18oC.
    It is sticky a lot and still leaves a little bit of color when you touch it.
    I tried to push it a little bit more to see if it goes all over the layers of gelcoat but it doesn't..
    The first layer or so seems cured or at least hard enough.
    Is there a way to solve this somehow to avoid scrape it off and reapply?

    Thanks
     
    Last edited: Nov 16, 2021
  2. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    Removing it and starting over is really the only option.

    If the layer against the mold is fully cured, and it must be fully cured to do this. You can catalyze some resin and brush it on the tacky surface, do this rather aggressively so it penetrates the soft gel coat as much as possible. Once cured you can blow it off with an air nozzle.

    If you try this and the layer against the mold isn't fully cured, then you have just bonded the gel coat to the mold and created a huge project.

    When gel coat is applied to a mold surface and doesn't cure in the normal amount of time it can eat through the mold release. Then when it does cure it will bond very well to the mold. Now you end up sanding all that gel coat off the mold to make it usable again.

    If you continue on and make the part and it sticks to the mold, you now have layers of glass that somehow need to be removed too. Many molds are disposed of at that point.

    If the part you made does come out of the mold, then the gel coat may fail soon due to improper catalization and a poor cure.

    On the other other hand, you may get lucky and everything works out perfectly.

    While very messy, cleaning the uncured gel coat off with squeegees, rags and plastic scrapers is the safest option.
     
    Last edited: Nov 16, 2021
    hoytedow likes this.
  3. mrdebian
    Joined: Apr 2021
    Posts: 26
    Likes: 4, Points: 3
    Location: Greece

    mrdebian Junior Member

    @ondarvr thanks a lot for your detailed explanation. Something similar happened in the past and I was able to release the kayak from the mold without a problem. It left a tiny bit of gelcoat here and there but was easily removed from the mold. The item (hull) however was a mess and had to fix the gelcoat but at least I didn't throw it and has been used in the sea for many hundreds of miles without a problem or at least yet.
    The one that I got now is nearly identical with the one that happened in the past in terms of how sticky it is so I believe I will try your first suggestion.
    What I didn't understand is the "Once cured you can blow it off with an air nozzle". What do you mean by saying this?
     
  4. ondarvr
    Joined: Dec 2005
    Posts: 2,709
    Likes: 426, Points: 83, Legacy Rep: 506
    Location: Monroe WA

    ondarvr Senior Member

    Hard gel coat can easily be blown off the mold with minimal effort. This method is quick and does no damage to the mold. Scraping and picking at the gel coat can result in scratching the mold. Now you can start over from the beginning knowing it will work.

    Or, after getting the gel coat cured with resin you can make the part. I won't gamble on it working when someone asks me about it, I don't want to influence them to take the risk. Making that decision for yourself is fine.
     
  5. kapnD
    Joined: Jan 2003
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    Location: hawaii, usa

    kapnD Senior Member

    You could waste a layer of mat/resin on it, and have better chances of pulling it off in big sheets.
    Any way, you’ll be much wiser to remove it and start fresh.
     
  6. Blueknarr
    Joined: Aug 2017
    Posts: 1,232
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    Location: Colorado

    Blueknarr Senior Member

    What I didn't understand is the "Once cured you can blow it off with an air nozzle". What do you mean by saying this?

    If there is hard gel against the mold-
    It should release
    Compressed air should be able to get between the gelcoat and the mold.
    It will blow the gelcoat off in big potato chip like pieces
    No damage to mold.

    Try first
    As other techniques may damage mold.
     

  7. mrdebian
    Joined: Apr 2021
    Posts: 26
    Likes: 4, Points: 3
    Location: Greece

    mrdebian Junior Member

    Hi all and thanks for the valuable info.
    I end up putting a layer of cloth with resin and I was able to pull the item from the mold with zero damage. Just a tiny bit of cleaning in a very small area.

    Thanks a lot
     
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